The Sky This Week, 2017 June 20 - 27

Rites of Summer

Jupiter, with the Great Red Spot
imaged 2017 June 12, 02:24 UT in good seeing from Alexandria, Virginia

The Moon opens the week as a waning crescent in the morning sky, then returns to the evening after New Moon, which occurs on the 23rd at 10:31 pm Eastern Daylight Time. Look for Luna’s slender sliver near Venus on the morning of the 21st. She ends the week tucked up close to the bright star Regulus on the evening of the 27th.

The summer solstice occurs on the 21st at 12:24 am EDT. This event marks the beginning of astronomical summer and is one of the most important dates observed by ancient cultures all around the world. It is on this date that the Sun reaches its most northerly declination and is thus a very easy way to keep track of the annual cycle of the seasons. We can find examples of solstice markers among ancient ruins all across ancient sites in the Northern Hemisphere. Perhaps the most famous of these is Stonehenge, a complex megalithic ruin in southwestern England. This site was the focus of intense activity for over a thousand years, and its earliest development predates the time of the construction of the pyramids of Giza. Its main axis is aligned to the summer solstice sunrise, and there are many other astronomical alignments incorporated in its form. The area surrounding Stonehenge has many other stone and wooden circles, earthen barrows, and long hand-excavated "avenues" that align with the solstice sunrise. In the Americas, solstice alignments are common among the many ancient sites built by ancient cultures like the Maya and Toltecs. In the United States we find such alignments at sites such as Big Horn Medicine Wheel in Wyoming, Chaco Canyon in New Mexico, and Hovenweep National Monument in Colorado. At the time of this year’s solstice the center of the Sun’s disc will touch the Tropic of Cancer just north of Hong Kong on the coast of mainland China. Here in Washington we’ll experience the longest duration of daily sunlight for the year, with Old Sol above our horizon for 14 hours and 54 minutes. Welcome to summer!

If you’re out looking at the stars to welcome the solstice, look to the south during the midnight hour. You’ll see one of the most distinctive constellations in the sky hanging just above the southern horizon. Scorpius is easily recognized by the ruddy star Antares marking the Scorpion’s heart, a vertical row of blue second-magnitude stars to the west of Antares, and a long curving arc of stars dipping down toward the southern horizon. In mythology the lowly scorpion killed the boastful hunter Orion, so the two constellations, each marked by bright reddish stars, were placed at opposite sides of the sky so they would never appear in the sky at the same time.

Jupiter dominates the early evening sky, appearing just west of the meridian after sunset. The giant planet is best seen during twilight and the first hours of astronomical darkness, but he now sets at around 1:30 am so there’s only a limited window to catch a good view of him in the telescope. Watch the moon Callisto pass just north of the planet on the evening of the 20th. On the 23rd, the planet’s famous Great Red Spot, now sporting a prominent orange hue, transits the disc between 9:00 and 11:00 pm.

Saturn wallows in the southern sky throughout the night. The ringed planet crosses the meridian at around 12:30 am, but he never gets higher than 30 degrees above the horizon. Haze and humidity will hinder your view of the planet’s fainter moons, but you should still have a fine view of the wide-open rings in moments of steady air.

You’ll find Venus climbing up from the eastern horizon in the gathering morning twilight. She is very prominent by 5:00 am, and will continue to greet you from this relative position for the next several months. Look for the slim waning crescent Moon nearby on the morning of the 21st.